A large surge was observed on September 17, 1971 part of which, after travelling 200,000 km across the surface, returned to the surface to form a filament. The filament lasted about 30 minutes, then rose up and returned to the source of the surge. This was interpreted as the filling of a semi-stable magnetic trap. Analysis of the microwave radio burst showed it to have been produced by a source optically thick at 8,800 MHz, with area 4 (arc min)squared and T approximately 275,000 deg, N squared sub eV approximately 7 x 10 to the 48th power. The soft x-ray burst showed a component at 12 x 1,00.000 deg with N squared sub eV approximately 3 x 10 to the 48th power

Zirin, H.

English

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https://ntrs.nasa.gov/search.jsp?R=19760016048 2020-03-22T16:04:23+00:00Z
1	 _	 ^
CALIFORNIA INS -i ITUTE OF TECHNOLOGY
BIG BEAR SOLAR OBSERVATORY
HALE OBSERVATORIES
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(NASA -C` 147C90)	 PF0EUCT.ZCN	 4	 N76-2.136
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MAY 1978 w
RECEIVED
NASA M 4"Lw o,
`^ INPUT BRANCH \ I
PRODUCTION OF A SHORT-LIVED FILAMENT BY A SURGE
H. Zirin
BIG BEAR SOLAR OBSERVATORY, HALE OBSERVATORIES
CARNEGIE INSTITUTION OF WASHINGTON
CALIFORNIA INSTITUTE OF TECHNOLOGY
C
m.
February, 1976
BBSO #0154
- 2 -
ABSTRACT
A large surge was observed on September 17, 1971 part
of which, after travelling 200,000 km across the surface,
returned to the surface to form a °_ilament. The filament
lasted about 30 minutes, then rose up and returned to the
source of the surge. We interpret this as the filling of a
semi-stable magnetic trap.
Analysis of the microwave radio burst shows it to have
been produced by a source optically thick at 8800 MHz, with
area 4 (arc minC and T ^- 275,000°, NeV— 7 x 10 4'. The
soft X-ray burst shows a component at 12 x 10 6 deg with	 i
NeV N 3 x 10 4 '	 4
e
t
,^	 I
i
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1:0, d,
	
,a
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Surges are ephemeral phenomena, with little relationship
to filaments. Filaments, on the other hand, are long-lived
accumulations of material in magnetic "traps" in the magnetic
field in the solar atmosphere; they form slowly, presumably
from condensing coronal material. In the unusual case we
report here, a short-lived cloud, very much like a filament,
was formed by ejecta from a large surge. The "filament"
lasted about 30 minutes, then rose and returned to the source
of the surge. Although projection effects may deceive us,
several arguments convince us this is a bona fide filament.
The surge is illustrated in Fiqure 1 as observed with
the 10" refractor (it is in the 1971 Big Bear Show Film). The
development of the large-scale phenomenon may be seen in our
small-scale pictures in Figure 2. The peculiar contrast in
Figure 2 is due to the use of a Fabry Perot filter. The source
of the surge was a small complex satellite reqion which developed
on the leading edge of a large complex active region (Sept. 15).
It &eveloped from an emerginq flux region with normal magnetic
connections to a small plage crossed by two filaments in a
peculiar, sheared configuration. The filaments darkened
around 1515 (first frame); at 1523 the filament disappeared;
there was rapid boiling, twisting, and some expansion for 20
minutes, till, at 1544 a rapid brightening and acceleration
occurred. A briqht ball formed for a moment, cnincidinn with
the peak of the 2800 MHz burst; at 1546 outward motion hecame
4even more rapid. The large scale outward velocity was 300 km/sec.
Various loops and fibrils appeared and were rapidly swept
outward, straightening out with the flow. The flow continued
steadily for 20 minutes, the base of the surge eventually
turning dark. The dark outward flow is seen at tho upper left
of the 16 05 26 fr,- •^e (Fig. 1). At 1607 a second fibril erupted,
and the flare brightening and outward flow ended by 1638.
The highest parts observed crossed the limb, a projected
distance of 360,000 km, at 1614 UT. At about 1605 UT, an
additional, lower arm of the surge appeared, which appeared to
supply a growing condensation visible in Fi gure 2 near point (c),
16 15 43 UT,about 200,000 km from the source. Some of the
surge material appeared to curve left as well. By 16 18 08
a full-fledged filament appears at points (b) and (c) with
four legs of the familiar hedgerow type, and several bright
points at its base. The filament remained in place until
1634 UT, when it slowly rose and began to return to the source.
This process too.. about 30 minutes, with peak velocities of
115 km/sec measured. A number of short-lived bright points
were seen as the surge material appeared to impact the surface
(this is seen at b in the last frame of Fi g . 1). Note that
the point (c), which as unoccupied by material at the peak of
the life of the filament was filled both going at 16 15 43
and returning at 16 43 28. On the lar ge-scale frames (Fiq.l)
the flare appears to have ended by 1638; but at 1700 the
first returning downward falling material arrived. The infall,
accompanied by brighteninq, continued until 1730. But for a
5 -
period of about 30 minutes, the flare was over at its origin,
and the energy was Stored at the distant filament.
It is possible that the filament is merely a condensation
high above the surface, seen projected against the disk. But
several strong points suggest that a real filament i.e. a
stable suspension of gas above the surface is seen. These
are:
1) The filament material is much darker than the surge
material; in fact it is darker than all the other
filaments on the disk.
2) The emission points observed can only be at the
surface. No such bright points have ever been observed
with a broad pass filter against the disk at the
top of the surge trajectory; there is simply not
enough density to excite Ha by collisions.
3) Material travelling at 300 km/sec abruptly stops,
increases in absorption and remains motionless for
thirty minutes. Such behavior can only be ascribed
to an encounter with a magnetic trap.
4) The filament formed shows the typical filament
fibril structure.
The following points arque against the identification of
t
the feature as a filament:
5) An absorption feature "q", 16 43 28 is seen near
•	 the S polar filament. This feature returns at the
same time as the "filament" rises. As it is not
very dark, and near the end of the surqe trajectory,
-M
- 6 -
it represents material near the top of the trajectory
which simply falls back, and apply the same argument
to the filament. However, we cannot explain why
this material remains stationary for fifteen minutes.
6)	 The location of the "filament" is an undistinguished
area of chromospher.ic network. No filament channel
is seen. However the other polar filaments don't
show filament channels either.
I have examined the Mt. Wilson magnetogram for this day,
but find the magnetic fields in this region too weak for
reliable field measurement. The magnetograms show overall
negative polarity but the Presence of several polar filaments
in the Hu pictures show the presence of several field reversals.
One can infer the presence of a neutral line by the following
argument: The south polar field at that time was minus (R.
Howard, private communication). A polar filament (f) is seen
in the region directly S of our "filament". This means that
the field is plus N of the polar filament. But the Mt. Wilson
magnetogram shows the area around the base of the surge to be
minus polarity. 'Thus there must be another neutral line between
the active region and the polar filament, and this may be the
line along where the filament forms (although we have absolutely
no proof that it is).
I have marked on the early frames of Fiqure 2 several
(pc,ints a,b,c) of the chromospheric features at the point
where the filament lands. They are, so far as we can tell,
- at,
- 7 -	 RhTROPUCIBIT.ITY OF T W
ORIGINAL PAGE IS PO ^!'
ordinary parts of the chromospheric network, although the
point b may be an ephemeral active region.
The various brightenings observe=d, although not perfectly,
understood, are reasonable. The lower edge of the surge is
brightened by Doppler-shifted nhotospheric emission (Zirin,
1969). The impact brightenings late in the event are not the
same as the effect discussed by Hyder (1967), who felt they
might produce a flare, but they do show that falling material
can produce minor brightening. In fact, if material falling
from such great heights can only produce these small brightenings,
it is hard to see how flares could be produced. The energy
of the returning material must be stored in t`1(,^ supporting
magnetic field; however in some way as equilibrium must be
reached which permits the matter to remain motionless for some
time. Presumably the compressed field reaches a stable state,
but bounces back when sufficient material leaks out of the
filament. In the stationary state the field is compressed by
the weight of the material; for a density of 10 10 and a column
10,000 km high, the pressure is about 0.5 erg/cm', and easily
sustained by a 5 gauss field. Tf this pressure is reached by
a compression of the field over the same 10,000 km (i.e. com-
pression of field lines from 20,000 to 10,000 km) then the
expanding field can produce the observed return velocity of
100 km/sec if it does not have., to work against qravity. Tn
fact, the returning material rises but slightly, so the
phenomenon is energetically possible, but of course its true
nature is probably much more complex.
_	 8
The reader may perhaps wonder why I have dwelt so long
on the question of whether or not a true filament was formed.
The significance is that magnetic traps exist in the solar
atmosphere, and the fact that even dynamic material may be
captured by them shows how prominence material may easily
accumulate there in more typical, slower formation.
Important information may be gained from the radio
burst, which was most interesting. Multifreduency data from
Sagamore Hill was kindly furnished by Dr. Castelli, and 2800 MHz
records from NEL by Dr. Bleiweiss. There was an impulsive
low frequency burst at the flash phase, peaking at 1546 and
ending 1547. At high frequencies, however, only a gradual
rise and fall was seen, peaking at 1554 along with the soft
X-rays. Further, the peak fluxes were: 15,400 MHz - 11.1 sfu
(peak at 1554); 8900 - 9.7 sfu (peak at 1554); 4995 - 5.6 sfu
(peak at 1545) and 2695 - 3.5 sfu (peak at 1545). While the
impulsive burst can be non-thermal, the peak at 1554 can
only be due to a maximum in the area covered by the event.
In fact the area of Ha emission is at a maximum at 1554 and
falls sharply afterward. The hiuh-frequency flux can then
be explained by thermal emission; the area of Ha emission is
about 2 arc min. Since the flux is flat above 8800 MHz, we
set 7 = 1 at that frequency. With an area of 4 (arc min)'
we got Teff = 278,000°, and, with L = 84,000 km (2 arc min),
N e ti 3.5 x 10 9 and NeV = 7.3 x 10" e	On the other hand, if wr.
compare the soft X-ray burst reported by Solrad 9, we find,
I
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using the curves of Hudson and Ohki (1972) T
— 1.2 x 10 7
 deg,
NeV = 3x10 4 ". This hot component only produces 2 sfu of
emission and does not affect the measured flux.
We conclude that the late peal; in the microwave burst is
produced by the maximum in area of a plasma at 275,000 1
 which
is just optically deep at 8800 MlIz, and is accompanied by a
much hotter component of nearly equal emission measure at
1.2 x 10 7
 deg. Harvard reported a III GG burst at flash phase
and type II burst at 1555, as one might expect.
I would like to thank Drs. John Castelli and Max Bleiweiss
for providing the radio data. This work was supported by
NASA grant NGR 05 002 034 and NSF qrant GA 43467X.
RF.FF.RF.NC'Fq
Hudson, H.S. and Ohki, K.: 1972, Solar Phys. 23, 155.
Ryder, C.L.:	 1967, Solar Phys. 2, 49.
7 irin, H.:	 1969, Solar Phys. 7, 243
M.
- 10 -
FIGURE CAPTIONS
FIGURE 1:
Six stages in the surge eruption, photographed in ha
centerline with the 10" telescope.
15 18 33 The fibril or small filament (F) crossing the
plage at upper left expands and darkens. A
boiling commences, reaching intense bricThtness.
15 46 58 The hot presurge plasma has been formed. The
radio burst is reported to start at 1544, at
which time bri g htening becomes rapid.
15 49 30 Rapid outward flow - tangled knots appear and
are blown outwa--d. 	 !
15 54 37 Continued rapid outward flow. The surge is
not a single puff, but o.n enormous force
sweeping material outward. Peak of microwave
burst. Type II burst, 1556.
16 05 26 The sur ge is about over, but dark fibrils
still stretch outward.
17 03 55 At point B, a new brightening occurs as matter
flows back downward from the filament.
FIGURE 2:
15 58 13 The surge moves rapidly outward, with a bright
lower edge.
I11
16 04 03 A great core of outward moving material reaches
as f-; as the polar filament f.
	 I
16 15 43 Brighteninq is seen along the surface at
c, and dark material to the SW is beginninq
to condense. Most of the condensation is to
take place in the parallelogram formed by i.
cell boundaries a and b.
1,6 18 08 In these few minutes the new filament has
condensed, covering several supergranule
cells. The bright edges do not coincide with
a and b; allowing for projection we can guess
that the left (SW) edge is midway between a
and b, and the closer (Nl:) edge at c is on
this side of b, so the filament arches over the
cell boundary b.
16 27 08 The surge has disappeared, but a small blob
remains at its most distant point, just below
the "T" in Sept. We cannot tell if it is high
above the surface or near the polar filament. f.
The new filament at ab is unchanged.
16 43 28 The filament at ab has be gun to move back:. Most
of the ab area is empty and the filaient is
now at c; also the element q has disappeared.
16 57 48 Material continues to flow back toward the
spot group
17 08 18 All over, except for a bright remainder at the
base of the surge.
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Production of a short-lived filament by a surge

A large surge was observed on September 17, 1971, part of which, after travelling 200 000 km through the corona, returned to the surface to form a filament. The filament lasted about 30 min, then rose up and returned to the source of the surge. We interpret this as the filling of a semi-stable magnetic trap. 



The energetics of radio, X-ray, and surge expulsion are estimated. The radio spectrum and flux correspond to a thermal source of area 4 (arcmin)², T ∼ 190 000 K, N²_e V ∼ 7 × 10⁴⁸, which is optically deep at 8800 MHz. 



The soft X-ray source has T ∼ 12 × 10⁶ K, N²_e V ∼ 3 × 10⁴⁸; and if an equal mass is expelled in the surge, the kinetic energy of the surge is similar to the thermal energy of the X-ray source

Caltech Authors - Main

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PRODUCTION OF A SHORT-LIVED FILAMENT BY A SURGE 
H. ZIRIN 
Big Bear Solar Observatory, Hale Observatories, Carnegie Institution of Washington, 
California Institute of Technology 
(Received 26 March; in final form 5 August, 1976) 
Abstract. A large surge was observed on September 17, 1971, part of which, after travelling 200 000 km 
through the corona, returned to the surface to form a filament. The filament lasted about 30 min, then rose up 
and returned to the source of the surge. We interpret this as the filling of a semi-stable magnetic trap. 
The energetics of radio, X-ray, and surge expulsion are estimated. The radio spectrum and flux correspond 
to a thermal source ofarea 4 (arcmin)2 , T"' 190 000 K, N; V,...., 7 x 1048 , which is optically deep at 8800 MHz. 
The soft X-ray source has T,...., 12 x 106 K, N; V,...., 3 x 1048 ; and if an equal mass is expelled in the surge, the 
kinetic energy of the surge is similar to the thermal energy of the X-ray source. 
Surges are ephemeral phenomena, fast ejections of material. Filaments, on the other 
hand, are long-lived accumulations of material in magnetic 'traps' in the magnetic 
field in the solar atmosphere; they form slowly, presumably from condensing coronal 
material. In the unusual case we report here, a short-lived cloud, very much like a 
filament, was formed by ejecta from a large surge.The 'filament' lasted about 30 
min,then rose and returned to the source of the surge. Although projection effects 
may deceive us, several arguments convince us this is a bona fide filament. 
The surge is illustrated in Figure 1 (Stop, E right on all pictures) as observed with 
the 10" refractor (it is in the 1971 Big Bear Show Film). The development of the large-
scale phenomenon may be seen in our small-scale pictures in Figure 2. The peculiar 
contrast in Figure 2 is due to the use of a Fabry-Perot filter. The source of the surge 
was a small complex satellite region which developed on the leading edge of a large 
complex active region (September 15). It developed from an emerging flux region 
with normal magnetic connections into a small plage crossed by two filaments in a 
peculiar, sheared configuration. The filaments darkened around 1515 (first frame); at 
1523 the filament disappeared; there was rapid boiling, twisting, and some expansion 
for 20 min, till, at 1544 a rapid brightening and acceleration occurred. A bright ball 
formed for a moment, coinciding with the peak of the 2800 MHz burst; at 1546 
outward motion became even more rapid. The large scale outward velocity was 
300 km s - 1 . Various loops and fibrils appeared and were rapidly swept outward, 
straightening out with the flow. The flow continued steadily for 20 minutes, the base 
of the surge eventually turning dark. The dark outward flow is seen at the upper left 
of the 160525 frame (Figure 1 ). At 1607 a second fibril erupted, and the flare 
brightening and outward flow ended by 1638. 
The highest parts observed crossed the limb, a projected distance of 360 000 km, at 
Solar Physics 50 (1976) 399-404. All Rights Reserved 
Copyright © 1976 by D. Reidel Publishing Company, Dordrecht-Holland 
© Kluwer Academic Publishers • Provided by the NASA Astrophysics Data System 
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Fig. 1. Six stages in the surge eruption, photographed in Ha centerline with the 1 O" telescope. 151833: 
The fibril or small filament (F) crossing the plage at upper left expands and darkens. A boiling commences, 
reaching intense brightness. 154658: The hot presurge plasma has been formed. The radio burst is reported 
to start at 1544, at which time brightening becomes rapid. 154930: Rapid outward flow - tangled knots 
appear and are blown outward. 155437: Continued rapid outward flow. The surge is not a single puff, but 
an enormous force sweeping material outward. Peak of microwave burst. Type II burst, 1556. 160526: The 
surge is about over, but dark fibrils still stretch outward. 170355: At point B, a new brightening occurs as 
matter flows back downward from the filament. 
© Kluwer Academic Publishers • Provided by the NASA Astrophysics Data System 
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PRODUCTION OF A SHORT-LIVED FILAMENT BY A SURGE 401 
1614 UT. At about 1605 UT, an additional, lower arm of the surge appeared, which 
appeared to supply a growing condensation visible in Figure 2 near point (c), 
161543 UT, about 200 000 km from the source. Some of the surge material appeared 
to curve left as well. By 161808 a filament-like feature appears at points (b) and (c) 
with four legs of the familiar hedgerow type, and several bright points at its base. The 
filament remained in place until 1634 UT, when it slowly rose and began to return to 
the source. This process took about 30 min, with peak velocities of 115 km s - 1 
measured. A number of short-lived bright points were seen as the surge material 
appeared to impact the surface (this is seen at Bin the last frame of Figure 1). Note 
that the point (c), which was unoccupied by material at the peak of the life of the 
filament, was filled both going at 161543 and returning at 164328. On the large-scale 
frames (Figure 1) the flare appears to have ended by 1638; but at 1700 the first 
returning downward falling material arrived. The infall, accompanied by brightening, 
continued until 1730. But for a period of about 30 min the flare ended, and no energy 
was being released; yet energy was available, perhaps stored in the new filament, to 
return it to its origin. 
It is possible that the filament is merely a condensation in the surge, high above the 
surface, and it only appears by projection to be a surface filament, and then falls 
back. But several strong points suggest that a real filament, i.e. a stable suspension of 
gas close to the surface, is seen. These are: 
(I) After 161543 the filament material is much darker than the surge material; in 
fact it is darker than all the other filaments on the disk. 
(2) The emission points observed can only be at the surface. It is very unlikely that 
any part of a suspended surge could be dense enough to emit Hc.t in projection against 
the disk. The emission points are similar to those usually seen at the feet of well-
established quiescent filaments. 
(3) Material travelling at 300 km s - i abruptly stops, increases in absorption and 
remains motionless for thirty minutes. This is hard to understand at the top of the 
surge trajectory but reasonable if it falls to the surface and accumulates in a magnetic 
trap. 
( 4) The filament formed shows the typical filament fibril structure. 
The following points argue against the identification of this feature as a filament: 
(5) An absorption feature 'g', 164328 is seen near the Spolar filament. This feature 
returns at the same time as the 'filament' rises. As it is not very dark, and near the end 
of the surge trajectory, it represents material near the top of the 'trajectory which 
simply falls back. So possibly the dark filament material is similar. 
(6) The location of the 'filament' is an undistinguished area of chromospheric 
network. No filament channel is seen. However the other polar filaments don't show 
filament channels either. 
I have examined the Mt. Wilson magnetogram for this day, but find the magnetic 
fields in this region too weak for reliable field measurement. There are several field 
reversals between pole and active regions but we can say nothing about the field 
where the filament formed. 
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402 H. ZIRIN 
8tG BEAR SOLAR OllllftVATOflY SEPT.17 .. 1971 
Fig. 2. 155813: The surge moves rapidly outward, with a bright lower edge. 160403: A great core of 
outward moving material reaches as far as the polar filament f 161543: Brightening is seen along the 
surface at c, and dark material to the SW is beginning to condense. Most of the condensation is to take 
place in the parallelogram formed by cell boundaries a and b. 161808: In these few minutes the new 
filament has condensed, covering several supergranule cells. The bright edges do not coincide with a and b; 
allowing for projection we can guess that the left (SW) edge is midway between a and b, and the closer 1(NE) 
edge at c is on this side of b, so the filament arches over the cell boundary b. 162708: The surge has 
disappeared, but a small blob remains at its most distant point, just below the' T' in Sept. We cannot tell if 
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PRODUCTION OF A SHORT-LIVED FILAMENT BY A SURGE 403 
I have marked on the early frames of Figure 2 (several points a, b, c) of the 
chromospheric features at the point where the filament lands. They are, so far as we 
can tell, ordinary parts of the chromospheric network, although the point b may be 
an ephemeral active region. 
The various brightenings observed, although not perfectly understood, are 
reasonable. The lower edge of the surge is brightened by Doppler-shifted 
photospheric emission (Zirin, 1969). The transient brightenings where material 
appears to hit the surface are not quite the effect discussed by Hyder (1967), who felt 
falling material might produce a flare, but they do show that such material can 
produce minor brightening. In fact, if material falling from such great heights can 
only produce these small brightenings, it is hard to see how flares could be produced. 
It is possible that the kinetic energy of the returning filament material has been stored 
in the magnetic field which traps it; however in some way as equilibrium must be 
reached which permits the matter to remain motionless for some time. A 5 or 10 gauss 
supporting field is entirely adequate to supply the necessary energy. 
The reader may perhaps wonder why I have dwelt so long on the question of 
whether or not a true filament was formed. The significance is that magnetic traps 
exist in the solar atmosphere, and the fact that even dynamic material may be 
captured by them shows how prominence material may easily accumulate there in 
more typical, slower formation. 
A rough idea of the energetics of this event can be obtained by radio and X-ray 
data at the beginning. Multi-frequency data from Sagamore Hill was kindly 
furnished by Dr Castelli, and 2800 MHz records from NEL by Dr Bleiweiss. There 
was an impulsive low frequency burst at the flash phase, peaking at 1546 and ending 
at 1547. At high frequencies, however, only a gradual rise and fall (grf) was seen, 
peaking at 1554 along with the soft X-rays. Further, the peak fluxes were: 15 400-
11.1 sfu (peak at 1554); 8800-9.7 sfu (peak at 1554); 4995-5.6 sfu (peak at 1545) and 
2695-3.5 sfu (peak at 1545). While the impulsive burst can be nonthermal, the peak at 
1554 occurs simultaneously with the peak in Ha area of the surge. After 1554, the 
area of the bright surge falls sharply. Therefore, we assume that the high frequency 
flux can be explained as thermal emission. The area of Ha emission is about 
(2 arc min) 2 . Since the flux is flat above 8800 MHz, we set r = 1 at that frequency. 
With an area of 4 (arcmin)2 , we get T0rr=191 OOOK, and, with L=87000km 
(2 arcmin), Ne""'3.5xl09 , NeV=2.3xl039, and N1V=8.lxl048 . The soft X-ray 
burst reported by Solrad 9 gives, using the curves of Culhane and Acton (1970), 
T""'l.2x 107 K, N;V=3x 1048 . This hot component only produces 2 sfu of radio 
emission; but if we assume the density of the hot component does not exceed that of the 
it is high above the surface or near the polar filament I The new filament at ab is unchanged. 164328: The 
filament at ab has begun to move back. Most of the ab area is empty and the filament is now at c; also the 
element g has disappeared. 165748: Material continues to flow back toward the spot group. 170818: All 
over, except for a bright remainder at the base of the surge. 
© Kluwer Academic Publishers • Provided by the NASA Astrophysics Data System 
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cooler, i.e. Ne= 3 x 109 , then Ne V = 1039 for the soft X-ray source and the total thermal 
energy for that source is 1.4 x 1030 ergs. If we assume the thermal energy of the X-ray 
source is in equipartition with the kinetic energy of the surge at 300 km s - 1, we find the 
mass of the surge must be 1.4 x 1015 gm, or Ne V ~ 1039 . Of course we cannot confirm 
the mass of the surge by any other way, but the result is reasonable. 
The microwave grf is thus produced by the maximum in area of a plasma at 
190 000 K which is just optically deep at 8800 MHz: This plasma is accompanied by a 
much hotter component of nearly equal emission measure at 1.2 x 10 7 K, and, if an 
equal amount of matter is involved in the surge, the surge kinetic energy is roughly 
equal to the thermal energy of the X-ray source. This energy is dissipated in the surge, 
but some may be stored temporarily in the short-lived filament. 
Acknowledgement 
I would like to thank Drs John Castelli and Max Bleiweiss for providing the radio 
data. This work was supported by NASA grant NGR 05 002 034, NSF grant 
ATM74-13489 and Air Force Contract F19628-76-C-0055. 
References 
Culhane, J. L. and Acton, L. W.: 1970, Monthly Notices Roy. Astron. Soc. 151, 141. 
Hyder, C. L.: 1967, Solar Phys. 2, 49. 
Zirin, H.: 1969, Solar Phys. 1, 243. 
© Kluwer Academic Publishers • Provided by the NASA Astrophysics Data System 


Production of a short-lived filament by a surge

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